For now there are no way to install clean build of MacOS Mojave if you are not under beta developer Apple program but we have a chance to switch default update Chanel to developer version.
All you need is a MacOS Developer Beta Access Utility attached this post and updated latest Clover EFI build with all needed for you system kexts placed on Other directory.
For example I use ASUS K541UV based Hackintosh to install Mac OS Mojave 10.14 over pre installed Mac OS High Sierra 10.13.
Run package file from attached dmg and wait until execution ends. Then in opened AppStore window thats should be show MacOS Mojave download section press download button and wait for load distro are done.
The simplest way is plain install from Application thats should be run after download complite and strongest way is a creating bootable USB drive and install from it with reboot. So, if you just wont test the system you have to do plain install.
After process are done when you computer reboot first time you have to chose Intsaller option from Clover menu and with next reboot you have to choose Firevault boot option thats synonym of boot MacOS option because it need less button presses ;)